Process for producing lactam

ABSTRACT

A method for producing a lactam, which comprises subjecting an alicyclic primary amine to an oxidation reaction in the presence of a catalyst comprising a silicon oxide, to thereby obtain a lactam. A catalyst comprising a silicon oxide which is for use in the above-mentioned method.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method for producing a lactamby oxidizing an alicyclic primary amine. More particularly, the presentinvention is concerned with a method for producing a lactam, whichcomprises subjecting an alicyclic primary amine to an oxidation reactionin the presence of a catalyst comprising a silicon oxide, to therebyobtain a lactam. In addition, the present invention also relates to acatalyst comprising a silicon oxide, which is for use in theabove-mentioned method. The method of the present invention not onlyprevents the by-production of ammonium sulfate which is of littlecommercial value, but also needs no cumbersome operations involved inconventional methods for producing a lactam, such as synthesis ofhydroxylamine salt (which can be obtained only by a process involvingcomplicated steps) and circulation of a buffer solution, and involves nostep of producing an intermediate oxime, which should be followed by anoxime purification operation, and, hence, a lactam can be produced froman alicyclic primary amine very easily.

[0003] 2. Prior Art

[0004] In the field of organic chemical industry, lactams are compoundsuseful as raw materials for polymers, pharmaceuticals, agriculturalchemicals and the like. In the case of ε-caprolactam, this compound hasbeen used for producing fibers and resins, and is especially useful as araw material for nylon 6.

[0005] Various processes for producing lactams, such as ε-caprolactam,are conventionally known. As examples of such conventional processes,there can be mentioned the processes described in “Kougyou Yuuki Kagaku(Industrial Organic Chemistry)”, fourth edition, page 240 (1976),written by von Klaus Weissermel and Hans-Jurgen Arpe, translated undersupervision of Teruaki Mukaiyama, TOKYO KAGAKU DOZIN CO., LTD., Japan(von Klaus Weissermel und Hans-Jurgen Arpe, “INDUSTRIELLE ORGANISCHECHEMIE”, Verlag Chemie Gmbh (1976)), which processes include:

[0006] (A) cyclohexanone oxime process in which cyclohexanone oxime issynthesized directly or through an intermediate compound (cyclohexanone)from cyclohexane, and the synthesized cyclohexanone oxime is subjectedto Beckman rearrangement, to thereby obtain ε-caprolactam;

[0007] (B) cyclohexanecarboxylic acid process in which toluene isoxidized in air to produce benzoic acid, the produced benzoic acid ishydrogenated to produce cyclohexanecarboxylic acid, and the producedcyclohexanecarboxylic acid is reacted with nitrosylsulfuric acid in thepresence of fuming sulfuric acid, to thereby obtain ε-caprolactam;

[0008] (C) caprolactone process in which cyclohexanone is oxidized withperacetic acid to produce ε-caprolactone, and the producedε-caprolactone is reacted with ammonia to thereby obtain ε-caprolactam;and

[0009] (D) nitrocyclohexanone process in which cyclohexanone isacetylated to obtain cyclohexenyl acetate, the obtained cyclohexenylacetate is nitrated to obtain 2-nitrocyclohexanone, the obtained2-nitrocyclohexanone is subjected to hydrolysis, thereby causing ringcleavage of the 2-nitrocyclohexanone to obtain nitrocapronic acid, theobtained nitrocapronic acid is hydrogenated to obtain ε-aminocapronicacid, and the obtained ε-aminocapronic acid is converted intoE-caprolactam.

[0010] Among the above-mentioned processes (A) to (D), the cyclohexanoneoxime process (A) and the cyclohexane carboxylate process (B) have beenpracticed on a commercial scale. Especially, the cyclohexanone oximeprocess (A) has been practiced worldwide and is the most important.

[0011] The representative method for producing a lactam by thecyclohexanone oxime process is a method in which cyclohexanone oxime isproduced from cyclohexanone and a hydroxylamine salt and, then,ε-caprolactam is synthesized from the produced cyclohexanone oxime bythe Beckman rearrangement performed using sulfuric acid. The Raschigprocess, which is a classical oximation process, involves the steps ofreducing ammonium nitrate using SO₂ to obtain a disulfonate, andhydrolyzing the obtained disulfonate to obtain a hydroxylamine salt ofsulfuric acid salt. The Raschig process practiced on a commercial scaleinvolves four steps which are very complicated. Further, in thisprocess, the amount of ammonium sulfate by-produced during the oximationperformed using the above-mentioned hydroxylamine salt of sulfuric acidsalt is approximately two moles per mole of the finally produced lactam.When the amount of ammonium sulfate by-produced in the Beckmanrearrangement performed using sulfuric acid is also taken intoconsideration, the amount of ammonium sulfate by-produced in the Raschigprocess is approximately four moles per mole of the finally producedlactam. The commercial value of ammonium sulfate as a raw material for afertilizer is no longer high, and the necessity of disposal of theby-produced ammonium sulfate is a great disadvantage of this process.

[0012] In this situation, for suppressing the by-production of ammoniumsulfate, the hydroxylamine sulfate oxime process (HSO process) and thehydroxylamine phosphate oxime process (HPO process) have been proposed.

[0013] The HSO process (see, for example, U.S. Pat. Nos. 3,941,838 and4,031,139) involves oxidizing ammonia in the presence of aplatinum-containing catalyst to obtain NO, subjecting the obtained NO toreduction with hydrogen in the presence of a platinum-containingcatalyst using an ammonium hydrogensulfate/ammonium sulfate buffersolution to produce hydroxylammonium sulfate, and reacting the producedhydroxylammonium sulfate with cyclohexanone.

[0014] The HPO process (see, for example, U.S. Pat. Nos. 3,948,988 and3,940,442) involves oxidizing ammonia to obtain a nitric acid ion,subjecting the obtained nitric acid ion to reduction with hydrogen inthe presence of palladium as a catalyst using a phosphoricacid/monoammonium phosphate buffer solution to produce a hydroxylaminesalt of phosphoric acid, and reacting the produced hydroxylamine salt ofphosphoric acid with cyclohexanone.

[0015] Each of the above-mentioned HSO and HPO processes is advantageousin that the buffer solution is allowed to circulate between thecyclohexanone oxime production system and the hydroxylamine saltproduction system, so that by-production of ammonium sulfate can beprevented. However, each of the processes has the followingdisadvantages. The process involves a number of reaction steps.Furthermore, the step of circulating the buffer solution is complicated.

[0016] As another improved process, there is known a process involvingreacting cyclohexanone with ammonia and hydrogen peroxide in thepresence of a solid catalyst to obtain cyclohexanone oxime (see U.S.Pat. No. 4,745,221). This method is advantageous not only in that theproduction of hydroxylamine salt is not needed and, hence, thecirculation of the buffer solution is not needed, but also in thatammonium sulfate is not by-produced. However, in this method, althoughthe oximation is not accompanied by the by-production of ammoniumsulfate, ammonium sulfate is by-produced during the synthesis of alactam as long as the Beckman rearrangement of an oxime for obtainingε-caprolactam is performed using sulfuric acid.

[0017] Cyclohexanone oxime processes involving no step of producingintermediate cyclohexanone have also been practiced. As an example ofsuch processes, there can be mentioned the photo-nitrosylation processwhich involves reacting cyclohexane with a gaseous mixture of hydrogenchloride and nitrosyl chloride by light irradiation using a mercury lampto obtain an oxime. This method is advantageous in that ammonium sulfateis not by-produced. However, the method has the following disadvantages.Light is needed for the oximation, so that not only is a large amount ofpower needed for the oximation, but also maintenance of a mercury lampor the like used for irradiation of light is cumbersome.

[0018] As another example of the cyclohexanone oxime processes involvingno step of producing intermediate cyclohexanone, there can be mentioneda method which comprises subjecting cyclohexylamine to oxidation in thepresence of a catalyst in the liquid or gaseous phase to thereby obtaincyclohexanone oxime. This method is advantageous in that ammoniumsulfate is not by-produced.

[0019] However, although this method is not accompanied by theby-production of ammonium sulfate during the oximation step, ammoniumsulfate is by-produced during the synthesis of a lactam as long as theBeckman rearrangement of an oxime for obtaining ε-caprolactam isperformed using sulfuric acid.

[0020] In this situation, several attempts have been made to prevent theby-production of ammonium sulfate during the Beckman rearrangement. Forexample, a gaseousphase Beckman rearrangement reaction using a solidcatalyst is known as a Beckman rearrangement reaction which is free fromthe by-production of ammonium sulfate. In most cases, the gaseous-phaseBeckman rearrangement reaction is performed by a method in which anoxime is converted to ε-caprolactam in the gaseous phase in the presenceof a zeolite type catalyst in a fixed-bed reactor or fluidized-bedreactor. In this method, ammonium sulfate is not by-produced becausesulfuric acid is not used.

[0021] By combining the above-mentioned conventional processes, forexample, by combining the oximation of cyclohexanone using hydrogenperoxide and the gaseousphase Beckman rearrangement of the resultantoxime, it is possible to obtain a method for producing a lactam, whichis free from the by-production of ammonium sulfate and cumbersomeoperations, such as synthesis of hydroxylamine salts and circulation ofa buffer solution, and which does not consume a large amount ofelectricity for providing light energy to the reaction system. However,the above-mentioned method comprising the conventional processes has thefollowing disadvantages. In this method, the production of theintermediate oxime necessitates a purification process for oxime. Inother words, the solvent used in the oximation process, unreactedammonia and by-produced water must be separation-removed from theoximation reaction mixture before subjecting the produced oxime to thegaseous-phase Beckman rearrangement. In addition, the solid catalystused for the gaseous-phase Beckman rearrangement reaction is likely tobe poisoned by impurities by-produced in a trace amount and, therefore,a high degree purification of the oxime becomes necessary.

[0022] Thus, there has been no conventional method for producing alactam, which is free from the by-production of ammonium sulfate and thenecessity for cumbersome operations, such as synthesis of hydroxylaminesalts and circulation of a buffer solution, and which needs no oximepurification operation (i.e., which involves no step of producing anintermediate oxime).

SUMMARY OF THE INVENTION

[0023] In this situation, the present inventors have made extensive andintensive studies with a view toward developing a method which is freefrom the above-mentioned problems. As a result, it has surprisingly beenfound that the above-mentioned problems can be solved by a method forproducing a lactam, which comprises subjecting an alicyclic primaryamine to an oxidation reaction in the presence of a catalyst comprisinga silicon oxide, to thereby obtain a lactam. Based on this finding, thepresent invention has been completed.

[0024] Accordingly, it is an object of the present invention to providea method for producing a lactam, which solves the above-mentionedproblems and enables a very easy production of a lactam directly from araw material alicyclic primary amine without producing an intermediateoxime, wherein the method not only is free from the by-production ofammonium sulfate which is of little commercial value, but also needs nocumbersome operations involved in conventional methods for producing alactam, such as synthesis of hydroxylamine salt (which can be obtainedonly by a process involving complicated steps), circulation of a buffersolution) and oxime purification operation.

[0025] It is another object of the present invention to provide acatalyst for use in the above-mentioned method, which comprises asilicon oxide.

[0026] The foregoing and other objects, features and advantages of thepresent invention will be apparent from the following detaileddescription and appended claims.

DETAILED DESCRIPTION OF THE INVENTION

[0027] In one aspect of the present invention, there is provided amethod for producing a lactam, which comprises subjecting an alicyclicprimary amine to an oxidation reaction in the presence of a catalystcomprising a silicon oxide, to thereby obtain a lactam.

[0028] In another aspect of the present invention, there is provided acatalyst for use in producing a lactam by subjecting an alicyclicprimary amine to an oxidation reaction, which comprises a silicon oxide.

[0029] For easy understanding of the present invention, the essentialfeatures and various preferred embodiments of the present invention areenumerated below.

[0030] 1. A method for producing a lactam, which comprises subjecting analicyclic primary amine to an oxidation reaction in the presence of acatalyst comprising a silicon oxide, to thereby obtain a lactam.

[0031] 2. The method according to item 1 above, wherein the oxidationreaction is performed in the presence of molecular oxygen.

[0032] 3. The method according to item 1 or 2 above, wherein theoxidation reaction is performed in the gaseous phase.

[0033] 4. The method according to any one of items 1 to 3 above, whichfurther comprises separating the lactam from a reaction system of theoxidation reaction.

[0034] 5. The method according to any one of items 1 to 4 above, whereinthe catalyst further comprises at least one element selected from thegroup consisting of lithium, sodium, potassium, rubidium, cesium,magnesium, calcium, strontium, barium, titanium, zirconium, vanadium,niobium, tantalum, molybdenum, tungsten, manganese, iron, cobalt,nickel, copper, zinc, silver, boron, aluminum, gallium, tin, phosphorus,antimony and bismuth.

[0035] 6. The method according to any one of items 1 to 5 above, whereinthe catalyst is a zeolite.

[0036] 7. The method according to item 6 above, wherein the zeolite isselected from the group consisting of silicalite-1 and silicalite-2.

[0037] 8. The method according to any one of items 1 to 5 above, whereinthe catalyst comprises an amorphous silicon oxide as the silicon oxide.

[0038] 9. The method according to item 8 above, wherein the catalystfurther comprises aluminum.

[0039] 10. The method according to item 8 or 9 above, wherein theamorphous silicon oxide has mesopores.

[0040] 11. The method according to item 10 above, wherein the amorphoussilicon oxide having mesopores is selected from the group consisting ofMCM-41 and HMS.

[0041] 12. The method according to item 10 above, wherein the amorphoussilicon oxide having mesopores is produced by adding to a siliconalkoxide a quaternary ammonium salt.

[0042] 13. The method according to item 12 above, wherein the quaternaryammonium salt is cetyltrimethylammonium salt.

[0043] 14. The method according to any one of items 1 to 13 above,wherein the alicyclic primary amine is obtained by subjecting to anamination reaction at least one compound selected from the groupconsisting of an alicyclic alcohol and an alicyclic ketone.

[0044] 15. The method according to item 14 above, wherein at least apart of one or more by-products formed in the oxidation reaction isrecycled to a reaction system of the amination reaction.

[0045] 16. The method according to any one of items 1 to 13 above,wherein the alicyclic primary amine is cyclohexylamine, and the lactamis ε-caprolactam.

[0046] 17. The method according to item 14 or 15 above, wherein the atleast one compound selected from the group consisting of an alicyclicalcohol and an alicyclic ketone is selected from the group consisting ofcyclohexanol and cyclohexanone, the alicyclic primary amine iscyclohexylamine, and the lactam is ε-caprolactam.

[0047] 18. A catalyst for use in producing a lactam by subjecting analicyclic primary amine to an oxidation reaction, which comprises asilicon oxide.

[0048] 19. The catalyst according to item 18 above, which furthercomprises at least one element selected from the group consisting oflithium, sodium, potassium, rubidium, cesium, magnesium, calcium,strontium, barium, titanium, zirconium, vanadium, niobium, tantalum,molybdenum, tungsten, manganese, iron, cobalt, nickel, copper, zinc,silver, boron, aluminum, gallium, tin, phosphorus, antimony and bismuth.

[0049] 20. The catalyst according to item 18 or 19 above, which is azeolite.

[0050] 21. The catalyst according to item 20 above, which is a zeoliteselected from the group consisting of silicalite-1 and silicalite-2.

[0051] 22. The catalyst according to item 18 or 19 above, whichcomprises an amorphous silicon oxide as the silicon oxide.

[0052] 23. The catalyst according to item 22 above, which furthercomprises aluminum.

[0053] 24. The catalyst according to item 22 or 23 above, wherein theamorphous silicon oxide has mesopores.

[0054] 25. The catalyst according to item 24 above, wherein theamorphous silicon oxide having mesopores is selected from the groupconsisting of MCM-41 and HMS.

[0055] 26. The catalyst according to item 24 above, wherein theamorphous silicon oxide having mesopores is produced by adding to asilicon alkoxide a quaternary ammonium salt.

[0056] 27. The catalyst according to item 26 above, wherein thequaternary ammonium salt is cetyltrimethylammonium salt.

[0057] As explained above, several processes for producing acycloalkanone oxime by oxidizing an alicyclic primary amine have beenknown in the art.

[0058] As examples of conventional processes for oxidation ofcyclohexylamine using molecular oxygen as an oxidizing agent, there canbe mentioned a process in which the oxidation of cyclohexylamine isperformed in the liquid phase using, as a catalyst, a compound of atleast one metal selected from the group consisting of metals belongingto Group 4 (IVB) of the Periodic Table (i.e., Ti, Zr and Hf) (seeUnexamined Japanese Patent Application Laid-Open Specification No. Hei2-295956 (corresponding to EP 395046)); and a process in which theoxidation of cyclohexylamine is performed in the gaseous phase in thepresence of a solid catalyst comprising SiO₂ gel, γ-Al₂O₃, andoptionally WO₃ (see U.S. Pat. Nos. 4,337,358 and 4,504,681).

[0059] As examples of conventional processes for oxidation ofcyclohexylamine using hydrogen peroxide as an oxidizing agent, there canbe mentioned a process using a catalyst comprising at least one metalselected from the group consisting of Mo, W and U (see U.S. Pat. No.2,706,204); and a process in which a titanium silicalite or a vanadiumsilicalite is used as a catalyst (see Tetrahedron, Vol. 51 (1995), No.41, page 11305; and Catal. Lett., Vol. 28 (1994), page 263).

[0060] Further, as examples of conventional processes for oxidation ofcyclohexylamine using an organic hydroperoxide as an oxidizing agent,there can be mentioned a process using a catalyst comprising at leastone metal selected from the group consisting of Ti, V, Cr, Se, Zr, Nb,Mo, Te, Ta, W, Re and U (see U.S. Pat. No. 3,960,954).

[0061] However, none of the above-mentioned prior art documents describethat ε-caprolactam is formed by the above-mentioned methods. Therefore,the production of a lactam directly from an alicyclic primary amine byoxidation was conventionally not known.

[0062] The present inventors have for the first time found that a lactamcan be produced directly from an alicyclic primary amine withoutproducing an intermediate cycloalkanone oxime, and successfullydeveloped a method for producing a lactam which not only is free fromthe by-production of ammonium sulfate, but also needs no cumbersomeoperations including an oxime purification operation. Such a method is avery useful technique because it leads to a decrease in the cost for thelactam production operation as well as the cost for the lactamproduction facilities.

[0063] Hereinbelow, the present invention is described in detail.

[0064] It is preferred that the alicyclic primary amine used in themethod of the present invention is a saturated alicyclic primary amine.Specific examples of saturated alicyclic primary amines includecyclohexylamine, cyclooctylamine, cyclopentylamine, cycloheptylamine andcyclododecanylamine. Among them, cyclohexylamine is preferred. Further,an alicyclic group of the alicyclic primary amine may be substitutedwith a substituent which is inert under the reaction conditions employedin the method of the present invention. One example of such an inertsubstituent is an alkyl group. The alicyclic primary amine may besubstituted with one or more substituents. As an example of alicyclicprimary amines substituted with an alkyl group, there can be mentionedmethylcyclohexylamine.

[0065] Cyclohexylamine, which is a preferred alicyclic primary amine,can be produced by, for example, any of the following processes: directamination of cyclohexene with NH₃ (e.g., processes described inUnexamined Japanese Patent Application Laid-Open Specification No. Sho57-4948 (corresponding to EP 39918), Unexamined Japanese PatentApplication Laid-Open Specification No. Sho 64-75453 (corresponding toEP 305564), Unexamined Japanese Patent Application Laid-OpenSpecification No. Hei 9-194438 (corresponding to EP 785185), UnexaminedJapanese Patent Application Laid-Open Specification No. Hei 10-72409(corresponding to EP 802176), and Unexamined Japanese Patent ApplicationLaid-Open Specification No. Hei 10-291968 (corresponding to EP 846675));amination of cyclohexanol with NH₃ (e.g., processes described inExamined Japanese Patent Application Publication No. Sho 41-7575,Examined Japanese Patent Application Publication No. Sho 51-41627,Examined Japanese Patent Application Publication No. Sho 51-32601(corresponding to U.S. Pat. No. 3,520,933) and Unexamined JapanesePatent Application Laid-Open Specification No. Hei 6-1758); amination ofcyclohexanone with NH₃ (e.g., processes described in Examined JapanesePatent Application Publication No. Sho 43-4332, Examined Japanese PatentApplication Publication No. Sho 45-19897 (corresponding to U.S. Pat. No.3,519,061), Examined Japanese Patent Application Publication No. Sho45-19898); and hydrogenation of aniline, nitrobenzene, nitrocyclohexaneor the like.

[0066] With respect to the purity of cyclohexylamine, there is noparticular limitation, and the cyclohexylamine used in the presentinvention may contain a trace amount of any of organic compounds, suchas cyclohexanol, dicyclohexylamine, nitrocyclohexane andN-cyclohexylidene-cyclohexylamine, which are formed during varioussynthesis processes involved in the cyclohexylamine production, and/or atrace amount of water.

[0067] From the viewpoint of economical advantages, molecular oxygen ispreferred as an oxidizing agent used in the oxidation reaction performedin the method of the present invention. However, the oxidizing agent isnot limited to molecular oxygen. If desired, any other oxidizing agentsmay be used as the oxidizing agent. Examples of other oxidizing agentsinclude various peroxides, such as hydrogen peroxide and tertiaryperoxide.

[0068] The method of the present invention is performed in the presenceof a catalyst comprising a silicon oxide. It is preferred that thecatalyst further comprises at least one element selected from the groupconsisting of lithium, sodium, potassium, rubidium, cesium, magnesium,calcium, strontium, barium, titanium, zirconium, vanadium, niobium,tantalum, molybdenum, tungsten, manganese, iron, cobalt, nickel, copper,zinc, silver, boron, aluminum, gallium, tin, phosphorus, antimony andbismuth. In the present invention, the above-mentioned “at least oneelement” is frequently referred to as a “heterometal”. Among theabove-mentioned heterometals, aluminum is especially preferred.

[0069] Further, the catalyst may comprise a trace amount of impuritieswhich are derived from the raw materials used for producing thecatalyst.

[0070] With respect to the structure of the catalyst, the silicon oxideas a main component of the catalyst may have a crystalline structure oran amorphous structure.

[0071] A zeolite can be used as the catalyst comprising a crystallinesilicon oxide. Zeolites can be classified into natural zeolites andsynthetic zeolites, depending on the formation process thereof. Bothnatural and synthetic zeolites can be used as a catalyst in the presentinvention. Conventionally, the term “zeolite” is used as a generic termfor crystalline aluminosilic acid (alluminosilicate), but the zeolite asdefined in the present invention also encompasses a compound comprisingsubstantially no aluminum and composed only of a silicon oxide (e.g.,silicalite), a compound further comprising metal components other thanaluminum (e.g., metallosilicate) and the so-called “phosphate zeolite”.

[0072] Specific examples of natural zeolites include natrolite,gonnardite, edingtonite, analcime, leucite, yugawaralite, gismondine,paulingite, phillipsite, chabazite, erionite, faujasite, mordenite,ferrierite, mutinaite, tshernichite, heulandite, clinoptilolite,stilbite, cowlesite, roggianite, hsianghualite, gaultite, pahasapaiteand weinebeneite.

[0073] Specific examples of synthetic zeolites include an A typezeolite, ZK-4, ZK-21, ZSM-5, ZSM-11, ZSM-12, silicalite-1, silicalite-2,a β type zeolite, an X type zeolite, a Y type zeolite, EU-1, NU-87,UTD-1, CIT-5, ITQ-4, ITQ-7, SSZ-42, MCM-21, MCM-22, TS-1, TS-2, VS-1,VS-2, tantalum silicate, SAPO-11, SAPO-34, SAPO-37, SAPO-42 and SAPO-56.The zeolite may have a heterometal incorporated into the skeletallattice thereof or may contain a heterometal outside the skeletallattice thereof. As a general method for introducing a heterometal intothe skeletal lattice of a zeolite, there can be mentioned a method inwhich a heterometal is added to the raw materials for the zeolite. As ageneral method for obtaining a zeolite containing a heterometal outsidethe skeletal lattice, there can be mentioned an impregnation method.

[0074] Among the above-mentioned zeolites, silcalite-1 and silicalite-2are preferred.

[0075] With respect to silicalite-1, the synthesis method and crystalstructure have been reported by Flanigen et al. (see E. M. Flanigen etal., Nature, Vol.271, p.512 (1978)). Silicate-1 has an MFI structure asin the case of ZSM-5 which is an aluminosilicate. ZSM-5 comprises a unitcell having a structure represented by the formula:Na_(n)[Al_(n)Si_(96-n)O₁₉₂].xH₂O, and silicate-1 is a compoundcomprising a unit cell which is substantially the same as that of ZSM-5,except that Al is not contained therein. ZSM-5 has linear channels(pores formed by 10-membered rings having a diameter of from 0.56 nm to0.53 nm) extending along the b-axis and zigzag channels (pores formed by10-membered rings having a size of from 0.55 nm to 0.51 nm) extendingalong the a-axis, wherein the linear channels and zigzag channels areinterconnected with each other to thereby form a three-dimensionalchannel system.

[0076] As an example of the method for producing silicalite-1, which isbased on the technique described in the above-mentioned document, therecan be mentioned a method comprising mixing tetraethoxysilane, ethanoland hydrous tetrapropylammonium hydroxide to thereby obtain a mixture,and subjecting the obtained mixture to a hydrothermal synthesis at 100to 200° C.

[0077] With respect to silicalite-2, the synthesis method and crystalstructure have been reported by Bibby et al. (see D. M. Bibby et al.,Nature, Vol.280, p.664 (1979)). Silicate-2 has the MEL structure as inthe case of ZSM-11. The composition of the unit cell of ZSM-11 is thesame as that of ZSM-5, and ZSM-11 also has channels formed by10-membered rings; however, unlike ZSM-5, both of the channels extendingalong the a-axis and the channels extending along the b-axis are linear.Silicalite-2 has substantially the same structure as that of ZSM-11,except that Al is not contained therein.

[0078] As an example of the method for producing silicalite-2, which isbased on the technique described in the above-mentioned document, therecan be mentioned a method comprising providing a silicon oxide hydrateor teraethoxysilane as an Si source and tetrabutylammonium hydroxide asa template, and subjecting the Si source and the template to ahydrothermal synthesis at around 170° C. The use of tetrabutylammoniumhydroxide is important for synthesizing silicalite-2, becausesilicalite-2 cannot be synthesized using any of other ammoniumhydroxides, such as tetraethylammonium hydroxide, tetrapropylammoniumhydroxide, triethylpropylammonium hydroxide and triethylbutylammoniumhydroxide.

[0079] With respect to the catalyst used in the method of the presentinvention, which comprises an amorphous silicon oxide, it is preferredthat the amorphous silicon oxide has the so-called “mesopores”. The term“pores” herein means small voids present on the surface of the catalystor inside the catalyst. With respect to the classification of the pores,it has been internationally agreed to classify the pores into thefollowing categories, based on the pore diameter thereof: submicropores(pore diameter<0.8 nm), micropores (0.8 nm<pore diameter<2 nm),mesopores (2 nm<pore diameter<50 nm) and macropores (pore diameter>50nm) (see IUPAC-Manual of Symbols and Terminology for PhysicochemicalQuantities and Units, Butterworths, London (1972)). In the method of thepresent invention, among the catalysts comprising an amorphous siliconoxide having mesopores, it is preferred to use a catalyst having anarrow pore diameter distribution, namely a catalyst generally called a“mesoporous substance”(see Ono and Yajima ed., “Zeoraito no Kagaku toKougaku (Science and Technology of Zeolites)”, page 13, 2000, publishedby Koudansha Scientific, Japan). A mesoporous substance is a substancehaving pores which are larger than those of a microporous substance(such as a zeolite) and smaller than those of a macroporous substance,and it is characteristic of a mesoporous substance that, as mentionedabove, the pore diameter is in the range of from 2 to 50 nm, and thatthe pore diameter distribution is narrow such that the diameters of thepores are almost the same.

[0080] The pore diameter distribution can be determined by variousmethods, such as mercury porosimetry and gas adsorption method. Withrespect to the determination of the pore diameter distribution ofmesopores, it is generally considered to be appropriate to employspecific gas adsorption methods, such as the BJH method, the DH methodand the MP method. The BJH method is employed in the Working Examples ofthe present invention. In the BJH method, the pore diameter distributionof a porous substance is calculated from the gas adsorption isotherm onthe assumption that all of the pores of the porous substance arecylindrical. Specifically, the pore diameter distribution is determined,based on the peak profile of the differential distribution curveobtained from the data of the gas adsorption isotherm. For those whohave ordinary skill in the field where porous substances are used as acatalyst etc., the BJH method is a very popular method for determiningthe pore diameter distribution of a mesoporous substance. For example,the BJH method is described in S. J. Gregg and K. S. W. Sing,“Adsorption, Surface Area and Porosity”, Academic Press, London (1982).Further, it is characteristic of a mesoporous substance that, in apowder x-ray diffraction analysis of the substance, a sharp peak isobserved at around 2 to 3 in terms of the 2θ/deg value. Such mesoporousmaterials include FSM-16, MCM-41, MCM-48, MCM-50, SBA-1, SBA-2, SBA-3,HMS, MSU-1, MSU-2, SBA-11, SBA-12, MSU-V, MSU-3, SBA-15 and SBA-16.

[0081] One of the generally employed methods for preparing a mesoporoussubstance involves reacting a lamellar silicate with a mono(long chainalkyl)tri(short chain alkyl)ammonium salt, such as acetyltrimethylammonium salt. For example, FSM-16 can be produced by thismethod from kanemite which is a lamellar silicate. It is understood thata mono(long chain alkyl)tri(short chain alkyl)ammonium salt isintercalated between the layers of lamellar silicate and widens thespaces between the layers, thereby forming mesopores.

[0082] Another method for preparing a mesoporous substance involvesreacting a silica source, such as a silicate or an alkoxide, with asurfactant (which is called a “template” for producing a mesoporoussubstance), to thereby obtain an organic-inorganic mesostructure inwhich the silica source molecules are arranged around meso-size micellesof the surfactant. Although it depends on the type of the mesostructure,it is generally necessary to subject a mixture of the silica source andthe template to aging for a certain period of time to form theorganic-inorganic mesostructure. As a template, it is possible to usenot only a surfactant (such as an anionic surfactant, a cationicsurfactant or a nonionic surfactant), but also an alkylamine, analkyldiamine or the like. The template contained in a mesostructure canbe decomposed and removed by solvent extraction or calcination tothereby obtain a mesoporous substance.

[0083] Among the above-mentioned catalysts which are mesoporoussubstances, MCM-41 and HMS are preferred. MCM-41 is a mesoporous silicawhich was reported by Mobil Oil Company in 1992 (see C. T. Kresge etal., Nature, 359, 710 (1992)). As a method for producing a MCM-41 havingmesopores which are regularly arranged in a manner similar to thearrangement of beehive holes, there can be mentioned a method in which asilicon alkoxide (such as tetraethoxysilane) or SiO₂ is used as an Sisource and a quaternary ammonium salt having a long chain alkyl group(such as cetyltrimethylammonium bromide) is used as a template, and theSi source and the template are subjected to a hydrothermal synthesis at150° C. for 48 hours.

[0084] With respect to HMS, the synthesis method and structure werereported by Tanev et al. (see P. T. Tanev et al., Science, Vol.267,p.865 (1995)). The difference between the method for synthesizing MCM-41and the method for synthesizing HMS is that HMS is synthesized using analkylamine as a template. In the above-mentioned document, the aging inthe synthesis of HMS is performed at room temperature for 18 hours.

[0085] The template contained in the catalyst can be removed as follows.In the case of MCM-41, a quaternary ammonium salt (template) can beheat-decomposition removed by calcining MCM-41. In the case of HMS, anamine (template) can be extraction removed from HMS using ethanol andthe like and, therefore, HMS is advantageous in that the template can berecovered and recycled. HMS is also called a mesoporous silica having awormhole structure, and the structural difference between HMS and MCM-41is that the mesopores of HMS are arranged in disordered threedimensional wormlike arrays, whereas the mesopores of MCM-41 arearranged in a regular ordered arrays.

[0086] A heterometal can be introduced into a mesoporous substanceeither inside or outside the silica network. As an example of the methodwhich is generally employed for introducing a heterometal into thesilica network of a mesoporous substance, there can be mentioned amethod in which a heterometal is added to the raw materials for thecatalyst. As an example of the method which is generally employed forintroducing a heterometal into the outside of the silica network, therecan be mentioned an impregnation method.

[0087] The above-mentioned mesoporous substances are characterized inthat the mesoporous substances comprise an amorphous silicon oxidehaving mesopores and having a very narrow pore diameter distribution.The method of the present invention can also be performed by using acatalyst comprising an amorphous silicon oxide which has mesopores butis not a mesoporous substance, namely a catalyst which does not exhibita sharp pore diameter distribution in the meso range in a powder x-raydiffraction analysis. It is characteristic of the powder X-raydiffraction patterns of the mesoporous substance and the non-mesoporoussubstance having mesopores that the mesoporous substance exhibits asharp peak at about 2 to 3 in terms of the 2θ/deg value, whereas thenon-mesoporous substance having mesopores exhibits only a broad peakhaving low intensity. The difference of the method for producing amesoporous substance from the method for producing a non-mesoporoussubstance is that, as mentioned above, the long aging time is needed forproducing a mesoporous substance. Specifically, in the above-mentioneddocuments, the aging times necessary for producing MCM-41 and HMS are aslong as 48 hours and 18 hours, respectively.

[0088] A catalyst comprising an amorphous silicon oxide which hasmesopores but is not a mesoporous substance can be synthesized by amethod in which a template which is similar to that used for producing amesoporous substance is used but the aging time is shorter than used inthe production of the mesoporous substance. Examples of silica sourcesinclude a silicon alkoxide, namely alkoxysilanes (e.g.,tetraethoxysilane and tetramethoxysilane), slica gel and fumed silica.Among them, a silicon alkoxide is preferred.

[0089] A catalyst comprising a non-mesoporous amorphous silicon oxidehaving mesopores can be produced by adding a specific compound to theabove-mentioned silica source. Examples of such specific compoundsinclude surfactants, such as an anionic surfactant, a cationicsurfactant and a nonionic surfactant; alkylamines and alkyldiamines. Aquaternary ammonium salt which is a cationic surfactant is preferablyused, but a quaternary ammonium salt having no activity or only lowactivity as a surfactant can also be used. Examples of quaternaryammonium salts which can be used for producing a catalyst comprising anon-mesoporous amorphous silicon oxide having mesopores include ahydroxide, bromide and chloride of tetramethylammonium,tetraethylammonium, tetrapropylammonium and terabutylammonium; and ahydroxide, bromide and chloride of a quaternary ammonium having a longchain alkyl group as one of its four alkyl groups, such ascetyl(hexadecyl)trimethylammonium, cetyltriethylammonium,cetyldimethylethylammonium and octyldecyltrimethylammonium. Among these,cetyltrimethylammonium hydroxide is preferred. A template introducedinto the catalyst can be removed by solvent extraction or bydecomposition by calcination.

[0090] After mixing all of the raw materials for the catalyst with theabove-mentioned template, the resultant mixture is agitated to therebyperform an aging of the mixture. The time needed for aging by agitationis only about 1 hour or less. After the aging, the resultant mixture issubjected to drying and calcination. Of course, the aging may beperformed for more than 1 hour without causing any problems. Further, aheterometal may be introduced into the catalyst. The introduction of theheterometal can be performed by adding a heterometal to the Si source tothereby obtain a catalyst having the heterometal incorporated therein,or alternatively, by immersing a calcined catalyst into a solution orsuspension containing a heterometal to thereby obtain a catalyst havingthe heterometal carried thereon.

[0091] In the present invention, the oxidation reaction can be performedin the gaseous or liquid phase using a fixed-bed or slurry-bed reactor.The reaction can be performed in a continuous or batchwise manner. Whenthe oxidation reaction is performed in the liquid phase, the oxidationreaction can be performed in the presence of a solvent.

[0092] There is no particular limitation with respect to the solventused in the present invention. Specific examples of such solventsinclude C₁-C₁₀ alcohols (such as methanol and t-butanol), acetonitrile,benzene, toluene, dimethylformamide, dimethyl sulfoxide, triethylamine,dimethoxyethane, dioxane, diglyme and water.

[0093] The reaction conditions are appropriately determined, taking intoconsideration the type of the oxidizing agent used, the type of thecatalyst used and the like. In general, the reaction can be performedunder a pressure of from atmospheric pressure to 10 MPa and at atemperature of from room temperature to 350° C.

[0094] The reaction of the present invention can be performed in eitherthe liquid phase or gaseous phase, but it is generally performed in thegaseous phase. The reaction conditions for performing the reaction inthe gaseous phase are as follows. The reaction pressure is in the rangeof from atmospheric pressure to 5 MPa. When the reaction is performedunder reduced pressure, an apparatus for maintaining the reactionpressure at a reduced pressure becomes necessary, and when the reactionis performed under a pressure exceeding 5 MPa, a high reactiontemperature becomes necessary for performing the reaction in the gaseousphase and the amount of by-products is likely to be increased. Thereaction temperature for the method of the present invention is in therange of from 80° C. to 350° C. When the reaction temperature is lowerthan 80° C., it becomes difficult to perform the reaction in the gaseousphase, and when the reaction temperature is higher than 350° C., theamount of by-products is likely to be increased.

[0095] There is no particular limitation with respect to the oxidizingagent used in the present invention, as long as the oxidizing agent isstable and exhibits satisfactory vapor pressure under the reactionconditions employed. A preferred oxidizing agent is oxygen. Oxygen canbe used in combination with nitrogen gas. Air can be also used as theoxygen source. In general, the molar ratio of oxygen to an alicyclicprimary amine is in the range of from 0.1 to 20. When the molar ratio ofoxygen is less than 0.1, the conversion of an alicyclic amine and theyield of the produced lactam are likely to become lowered. When themolar ratio of oxygen exceeds 20, the amount of by-products is likely tobecome increased and the yield of the produced lactam is likely tobecome lowered.

[0096] The amount of an amine contained in a feedstock gas is 1 to 20vol %. The space velocity (SV) of the feedstock gas is 20 to 3000 hr⁻1.Needless to say, appropriate conditions for maintaining the gaseousphase vary depending on the type of the raw material amine used and thetype of the lactam produced and, therefore, the reaction pressure, thereaction temperature, the molar ratio of oxygen to the raw materialamine and the SV value should be appropriately selected from theabove-mentioned ranges so as to maintain the gaseous phase.

[0097] A lactam obtained by the oxidation reaction of an alicyclicprimary amine is generally obtained in the form of a reaction mixturecontaining unreacted raw material amine and oxidation by-products.Accordingly, it is preferred that the method of the present inventionfurther comprises a step for separating the produced lactam from areaction system of the oxidation reaction. When the alicyclic primaryamine is cyclohexylamine, the produced lactam is ε-caprolactam which ismainly used as a raw material for nylon 6 and, in general, is requiredto have a purity of not less than 99.9%. The obtained lactam can beseparated from the reaction system by a customary method, such asdistillation, extraction, crystal deposition, hydrogenation, ionexchange or treatment with activated carbon. These methods can beperformed individually or in combination to thereby obtaining a lactamhaving a desired purity. When the oxidation reaction is performed in agaseous phase and when both the conversion of the raw material amine andthe selectivity for lactam are close to 100%, the produced lactam can beseparated from the reaction system simply by removing the gas from thereaction system.

[0098] The alicyclic primary amine used in the method of the presentinvention is preferably a compound obtained by subjecting to anamination reaction at least one compound selected from the groupconsisting of an alicyclic alcohol and an alicyclic ketone. Further, inthe present invention, it is preferred that at least a part of one ormore by-products formed in the oxidation reaction of the alicyclicprimary amine is recycled to a reaction system of the above-mentionedamination reaction.

[0099] The reaction products formed in the oxidation reaction of analicyclic primary amine include not only lactam and unreacted rawmaterial amine, but also a cycloalkanone oxime, an alicyclic alcohol, analicyclic ketone, a condensate of an alicyclic alcohol and an alicyclicketone, and the like. In general, the unreacted amine can be recycled tothe reaction system of the oxidation reaction of an amine, and thecycloalkanone oxime can be converted into a lactam by a conventionalmethod. Further, the alicyclic alcohol, the alicyclic ketone and thecondensate thereof can be recycled to the reaction system of theamination reaction to convert these by-products into an alicyclicprimary amine which can be used as a raw material, thereby increasingthe yield of a lactam.

[0100] When the alicyclic primary amine used in the method of thepresent invention is cyclohexylamine and the produced lactam isε-caprolactam, cyclohexanol and cyclohexanone are formed as thealicyclic alcohol and the alicyclic ketone, respectively, and thesecompounds can be recycled to the reaction system of the aminationreaction.

[0101] In the method of the present invention, the amination reaction ofat least one compound selected from the group consisting of an alicyclicalcohol and an alicyclic ketone can be performed by a conventionalprocess.

[0102] For example, when at least one compound selected from the groupconsisting of cyclohexanol and cyclohexanone is used, the aminationreaction thereof can be performed by any of the following conventionalprocesses. Examples of conventional processes for performing theamination reaction of cyclohexanol include a process comprising reactingcyclohexanol with ammonia in a gaseous phase in the presence ofhydrogen, using copper oxide/zinc oxide as a catalyst (see“Kougyoukagakuzasshi (Journal of the Society of Chemical Industry)”,Vol. 70 (1967), No. 9, page 1508); a process comprising reactingcyclohexanol with ammonia in a gaseous phase in the presence ofhydrogen, under atmospheric pressure using a reduced nickel-containingshaped catalyst, wherein the reduced nickel is supported on diatomaceousearth (see Examined Japanese Patent Application Publication No. Sho51-41627); a process comprising reacting cyclohexanol with ammonia in aliquid phase at a high temperature in the presence of hydrogen under ahigh pressure using a catalyst comprised mainly of cobalt (see ExaminedJapanese Patent Application Publication No. Sho 51-32601); and a processcomprising reacting cyclohexanol with ammonia in the presence of water,using a ruthenium-containing catalyst (see Unexamined Japanese PatentApplication Laid-Open Specification No. Hei 6-1758).

[0103] Examples of conventional processes for performing the aminationreaction of cyclohexanone include a process comprising reactingcyclohexanone with ammonia in a gaseous phase in the presence ofhydrogen, using nickel, cobalt, platinum or paradium as a catalyst (seeChemical Abstract, 15, 1285, 1921); and process comprising reactingcyclohexanone with ammonia in a liquid phase in the presence ofhydrogen, using nickel as a catalyst (see “Kougyoukagakuzasshi (Journalof the Society of Chemical Industry)”, Vol. 70 (1967), No. 8, page1335).

[0104] Examples of conventional processes for performing the aminationreaction of a mixture of cyclohexanol and cyclohexanone include aprocess comprising reacting a mixture of cyclohexanol and cyclohexanonewith ammonia in the presence of hydrogen, using a nickel oxide/chromiumoxide catalyst (see French Patent No. 1,492,098); and a processcomprising reacting a mixture of cyclohexanol and cyclohexanone withammonia in a gaseous phase using a catalyst comprised of nickel and/orcobalt, and phosphoric acid or boric acid (see Examined Japanese PatentApplication Publication No. Sho 41-7575).

[0105] The amination reaction can be performed in the presence ofammonia and hydrogen using a catalyst.

[0106] As the amination catalyst, there can be mentioned various metals,metal oxides, metal salts and organo-metal compounds. It is preferredthat the amination catalyst comprises at least one metal selected fromthe group consisting of metals belonging to Groups 8, 9 and 10 of thePeriodic Table (such as Fe, Co, Ni, Ru, Rh, Pd, Ir and Pt), Cr, Cu, Ag,Zn and Al. The amination catalyst may comprise a single metal, aplurality of metals, or a metal compound(s) (such as a metal oxide), andthe catalyst may comprise a carrier having supported thereon any of theabove-mentioned metals or metal compounds. Examples of carriers includean activated carbon, SiO₂, Al₂O₃, SiO₂/Al₂O₃, TiO₂, ZrO₂, ZnO, bariumsulfate, potassium carbonate, diatomaceous earth and a zeolite.

[0107] The amination reaction can be performed in a gaseous or liquidphase using a fixed-bed, slurry-bed or fluidized-bed reactor. Thereaction can be performed in a continuous or batchwise manner.

[0108] When the reaction is performed in a liquid phase, a solvent canbe used. With respect to the solvent, there is no particular limitation.Examples of solvents include nitriles, such as acetonitrile andpropionitrile; aliphatic hydrocarbons, such as n-hexane and cyclohexane;aromatic compounds, such as benzene and toluene; ethers, such as dioxaneand diglyme; and water. When the amination reaction is performed in thepresence of a solvent, the amount of cyclohexanol is generally from 1 to30% by weight, preferably from 3 to 20% by weight, based on the totalweight of the alicyclic alcohol and the solvent. The solvent can also beused when the amination reaction is performed in a gaseous phase. Inthis case, the solvent can be introduced in a gaseous form into thereactor.

[0109] The amination reaction can be performed using a catalyst whichhas been pretreated with hydrogen. The use of a hydrogen-pretreatedcatalyst in the amination reaction is effective not only in that thecatalytic activity of the catalyst can be maintained for a long periodof time, but also in that the selectivity for and yield of an alicyclicprimary amine can be improved. The hydrogen-pretreatment of the catalystcan be performed by heating the catalyst in the presence of hydrogen inthe absence of a main raw material (i.e., alicyclic alcohol and/or analicyclic ketone) and in the absence or presence of a solvent. Theheating is generally performed at a temperature in the range of from 100to 500° C. The hydrogen-pretreatment can be performed in a batchwisemanner using an agitation reactor or in a continuous manner using atubular reactor.

[0110] In the amination reaction, the molar ratio of at least onecompound selected from the group consisting of an alicyclic alcohol andan alicyclic ketone:ammonia:water is generally from 1:1:1 to 1:10:10.The reaction conditions can be appropriately determined, taking intoconsideration the type of the reaction system, the type of the catalystused and the like. The reaction pressure is generally from 0.1 to 10 MPaand the reaction temperature is generally from 80 to 250° C.

[0111] The alicyclic primary amine produced by the amination reaction isrecovered from the reaction mixture in the reactor by any customarymethods, such as distillation and extraction, and if desired, thealicyclic primary amine is further subjected to treatment for isolation,thereby obtaining an alicyclic primary amine having a desired purity. Ingeneral, it is preferred that the alicyclic alcohol (or an alicyclicketone or a mixture thereof) which remains unreacted and the ammoniawhich remains unreacted (each of which is recovered from the reactor)can be recycled to the reactor of the amination reaction system.

BEST MODE FOR CARRYING OUT THE INVENTION

[0112] Hereinbelow, the present invention will be described in moredetail with reference to the following Examples and ComparativeExamples, which should not be construed as limiting the scope of thepresent invention.

[0113] In the following Examples and Comparative Examples, variousmeasurements were conducted using the following apparatuses.

[0114] Gas Chromatography (GC) Apparatus:

[0115] Gas chromatograph Model GC-14B (manufactured and sold by ShimadzuCorporation, Japan)

[0116] GC Column:

[0117] DB-1701 (manufactured and sold by J & W Scientific, U.S.A.)

[0118] Conditions for GC:

[0119] Injection temperature: 250° C.

[0120] Column temperature: Initially, the temperature was maintained at50° C. and, then, the temperature was elevated at a rate of 10° C./minto 250° C.

[0121] Powder X-Ray Diffraction Measuring Apparatus:

[0122] RAD-IIIA (manufactured and sold by Rigaku Corporation, Japan)

[0123] Energy Dispersive X-Ray Analysis System:

[0124] EMAX-5770W (manufactured and sold by Horiba Ltd., Japan)

[0125] Pore Size Distribution Measuring Apparatus:

[0126] Autosorb-3 MP (manufactured and sold by Quanta-chromeInstruments, U.S.A.)

EXAMPLE 1

[0127] <Catalyst: SiO₂ (1)>

[0128] To 71 g of tetraethoxysilane (Si(OC₂H₅)₄; manufactured and soldby Wako Pure Chemical Industries, Ltd., Japan) was added 125 g of water,and thereto was further added 10 ml of a 28% by weight aqueous ammoniawhile stirring. After adding 10 ml of ethanol to the resultant mixture,the stirring of the mixture was continued for 1 hour. Using a rotaryevaporator, the mixture was heated to dryness under reduced pressure inan oil bath at 120° C., thereby obtaining a dried product. The obtaineddried product was subjected to further drying in an electric kiln at120° C. for 12 hours, followed by calcination at 400° C. for 4 hours,thereby obtaining a solid catalyst. The catalyst was subjected to apowder X-ray diffraction analysis as described above. The results of theX-ray diffraction analysis showed that the catalyst was an amorphoussilicon oxide.

[0129] The above-obtained catalyst was charged into a reaction vessel(outer diameter: 12.7 mm, inner diameter: 9.0 mm, length: 100 mm) whichwas made of SUS316 and which was provided with conduits for introducingcyclohexylamine and molecular oxygen, respectively; a sheath tube forinserting a thermocouple therein, wherein the thermocouple was used tomeasure the temperature of a catalyst layer formed inside the reactionvessel; and a layer of SUS316 fillers for vaporizing cyclohexylamine.Then, the reaction vessel containing the catalyst was placed in aheating furnace. To the reaction vessel was attached a line forwithdrawing a part of a gaseous reaction mixture from an outlet of thereaction vessel and introducing the withdrawn reaction mixture into theGC apparatus, while maintaining the gaseous state of the reactionmixture. The gaseous reaction mixture introduced into the GC apparatusthrough the above-mentioned line was analyzed under the above-mentionedconditions. The conversion of cyclohexylamine and selectivity forε-caprolactam were calculated from the results of the GC analysis.

[0130] After purging the reaction vessel with nitrogen gas, the reactionvessel was heated to and maintained at 160° C. The reaction was startedby feeding cyclohexylamine and oxygen into the reaction vessel. Thefeeding of cyclohexylamine and oxygen was performed under conditionswherein the composition of the mixture of cyclohexylamine, oxygen andnitrogen around the inlet of the reaction vessel became: cyclohexylamine5.1% by volume, oxygen=6.6% by volume, and nitrogen=88.3% by volume, andwherein the SV value became 270 to 380 h⁻³. 20 Hours after the start ofthe reaction, the temperature of the reaction vessel was elevated to180° C. 25 Hours after the start of the reaction, the conversion ofcyclohexylamine was 17% and the selectivity for ε-caprolactam was 3%.

COMPARATIVE EXAMPLE 1

[0131] <Catalyst: Al₂O₃>

[0132] A reaction was performed in substantially the same manner as inExample 1, except that alumina (high purity alumina NRK-301,manufactured and sold by Nishio Industries, Japan) was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 180° C. at the point in time of 30 hoursafter the start of the reaction, further elevated to 200° C. at thepoint in time of 45 hours after the start of the reaction, and furtherelevated to 230° C. at the point in time of 49 hours after the start ofthe reaction. No ε-caprolactam was produced throughout the reaction.

EXAMPLE 2

[0133] <Catalyst: SiO₂ (2)>

[0134] To 71 g of tetraethoxysilane was added 125 g of water, andthereto was further added 0.1371 g of ammonium sulfate while stirring,followed by addition of 12.5 ml of a 28% by weight aqueous ammonia.After adding 10 ml of ethanol to the resultant mixture, the stirring ofthe mixture was continued for 1 hour. Using a rotary evaporator, themixture was heated to dryness under reduced pressure in an oil bath tothereby obtain a dried product, wherein the temperature of the oil bathwas initially maintained at 60° C. and elevated to 120° C. The obtaineddried product was subjected to further drying in an electric kiln at120° C. for 12 hours, followed by calcination at 400° C. for 4 hours,thereby obtaining a solid catalyst. The catalyst was subjected to apowder X-ray diffraction analysis as described above. The results of theX-ray diffraction analysis showed that the catalyst was an amorphoussilicon oxide.

[0135] A reaction was performed in substantially the same manner as inExample 1, except that the above-obtained catalyst was used as the solidcatalyst and the temperature of the reaction vessel was maintained at160° C. 21 Hours after the start of the reaction, the conversion ofcyclohexylamine was 21% and the selectivity for ε-caprolactam was 2%.

EXAMPLE 3

[0136] <Catalyst: SiO₂ (2)>

[0137] A reaction was performed in substantially the same manner as inExample 2, except that the temperature of the reaction vessel wasmaintained at 180° C. 8 Hours after the start of the reaction, theconversion of cyclohexylamine was 32% and the selectivity forε-caprolactam was 5%.

EXAMPLE 4

[0138] <Catalyst: V₂O₅/SiO₂>

[0139] To 0.383 g of ammonium metavanadate (NH₄VO₃; manufactured andsold by Wako Pure Chemical Industries, Ltd., Japan) were added 9.2 g ofwater and 26.5 g of a 10% by weight aqueous solution oftetrapropylammonium hydroxide ([(CH₃CH₂CH₂)₄N]OH; manufactured and soldby Wako Pure Chemical Industries, Ltd., Japan), followed by stirring,and thereto was further added 17.33 g of tetraethoxysilane whilestirring (Si/V atomic ratio=25). The stirring of the resultant mixturewas continued at room temperature for 5 hours. Using a rotaryevaporator, the mixture was heated to dryness under reduced pressure inan oil bath to thereby obtain a dried product, wherein the temperatureof the oil bath was initially maintained at 60° C. and elevated to 120°C. The obtained dried product was subjected to calcination at 550° C.for 4 hours, thereby obtaining a solid catalyst. The catalyst wassubjected to a powder X-ray diffraction analysis as described above. Theresults of the X-ray diffraction analysis showed that the catalyst wascomprised of an amorphous silica.

[0140] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, and the temperature of the reaction vessel was maintained at160° C. 28 Hours after the start of the reaction, the conversion ofcyclohexylamine was 2% and the selectivity for ε-caprolactam was 3%.

EXAMPLE 5

[0141] <Catalyst: MoO₃/SiO₂>

[0142] To 0.57 g of molybdenum trioxide (MoO₃; manufactured and sold byWako Pure Chemical Industries, Ltd., Japan) were added 9.2 g of waterand 26.5 g of a 10% by weight aqueous tetrapropylammonium hydroxidesolution, followed by stirring, and thereto was further added 17.33 g oftetraethoxysilane while stirring (Si/Mo atomic ratio=21). The stirringof the resultant mixture was continued at room temperature for 5 hours.Using a rotary evaporator, the mixture was heated to dryness underreduced pressure in an oil bath to thereby obtain a dried product,wherein the temperature of the oil bath was initially maintained at 60°C. and elevated to 120° C. The obtained dried product was subjected tocalcination at 550° C. for 4 hours, thereby obtaining a solid catalyst.The catalyst was subjected to a powder X-ray diffraction analysis asdescribed above. The results of the X-ray diffraction analysis showedthat the catalyst was comprised of an amorphous silica.

[0143] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 180° C. at the point in time of 19 hoursafter the start of the reaction, and further elevated to 200° C. at thepoint in time of 28 hours after the start of the reaction. 6 Hours afterthe start of the reaction, the conversion of cyclohexylamine was 3% andthe selectivity for ε-caprolactam was 1%; 26 hours after the start ofthe reaction, the conversion of cyclohexylamine was 5% and theselectivity for ε-caprolactam was 2%; and 42 hours after the start ofthe reaction, the conversion of cyclohexylamine was 15% and theselectivity for ε-caprolactam was 5%.

EXAMPLE 6

[0144] <Catalyst: TiO₂/SiO₂>

[0145] To 17.75 g of tetraethoxysilane were added 2.0 g of methanol and31.3 g of water while stirring, and thereto was further added 3.5532 gof titanium tetra-isopropoxide (Ti[OCH(CH₃)₂]₄; manufactured and sold byWako Pure Chemical Industries, Ltd., Japan) (Si/Ti atomic ratio=6).After adding 2.5 g of a 28% aqueous ammonia, the stirring of the mixturewas continued at room temperature for 1 hour. Using a rotary evaporator,the mixture was heated to dryness under reduced pressure in an oil bathto thereby obtain a dried product, wherein the temperature of the oilbath was initially maintained at 60° C. and elevated to 120° C. Theobtained dried product was subjected to calcination at 400° C. for 4hours, thereby obtaining a solid catalyst. The catalyst was subjected toa powder X-ray diffraction analysis as described above. The results ofthe X-ray diffraction analysis showed that the catalyst was comprised ofan amorphous silica.

[0146] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 180° C. at the point in time of 19 hoursafter the start of the reaction, and further elevated to 200° C. at thepoint in time of 28 hours after the start of the reaction. 12 Hoursafter the start of the reaction, the conversion of cyclohexylamine was8% and the selectivity for ε-caprolactam was 5%; 23 hours after thestart of the reaction, the conversion of cyclohexylamine was 8% and theselectivity for ε-caprolactam was 7%; and 31 hour after the start of thereaction, the conversion of cyclohexylamine was 9% and the selectivityfor ε-caprolactam was 15%.

EXAMPLE 7

[0147] <Catalyst: Al₂O₃/SiO₂ (1)>

[0148] To 15 g of tetraethoxysilane was added 10.0 g of aluminumsec-butoxide (Al[O(CH₃)CH(C₂H₅)]3; manufactured and sold bySigma-Aldrich Co., U.S.A) (Si/Al atomic ratio=1.8), followed bystirring, and thereto was further added 6.3 g of water while stirring.The stirring of the resultant mixture was continued at room temperaturefor 1 hour. Using a rotary evaporator, the mixture was heated to drynessunder reduced pressure in an oil bath at 120° C., thereby obtaining adried product. The obtained dried product was subjected to calcinationat 200° C. for 4 hours, thereby obtaining a solid catalyst. The catalystwas subjected to a powder X-ray diffraction analysis as described above.The results of the X-ray diffraction analysis showed that the catalystwas comprised of an amorphous silica.

[0149] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., and the temperature ofthe reaction vessel was elevated to 180° C. at the point in time of 32hours after the start of the reaction. 48 Hours after the start of thereaction, the conversion of cyclohexylamine was 15% and the selectivityfor ε-caprolactam was 5%.

EXAMPLE 8

[0150] <Catalyst: Al₂03/SiO₂ (2)>

[0151] To 180 g of tetraethoxysilane was added 6.0 g of aluminumsec-butoxide (Si/Al atomic ratio=35.5), and thereto was added 46.5 g ofwater while stirring. The resultant mixture was stirred at roomtemperature for 1 hour. Using a rotary evaporator, the mixture washeated to dryness under reduced pressure in an oil bath to therebyobtain a dried product, wherein the temperature of the oil bath wasinitially maintained at 80° C. and elevated to 120° C. The obtaineddried product was subjected to calcination at 200° C. for 4 hours,thereby obtaining a solid catalyst. The catalyst was subjected to apowder X-ray diffraction analysis as described above. The results of theX-ray diffraction analysis showed that the catalyst was comprised of anamorphous silica.

[0152] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 180° C. at the point in time of 21 hoursafter the start of the reaction, and further elevated to 200° C. at thepoint in time of 31 hours after the start of the reaction. 20 Hoursafter the start of the reaction, the conversion of cyclohexylamine was3% and the selectivity for ε-caprolactam was 13%; 25 hours after thestart of the reaction, the conversion of cyclohexylamine was 3% and theselectivity for ε-caprolactam was 28%; and 33 hours after the start ofthe reaction, the conversion of cyclohexylamine was 3% and theselectivity for ε-caprolactam was 42%.

EXAMPLE 9

[0153] <Catalyst: Al₂O₃/SiO₂ (3)>

[0154] To 120 g of tetraethoxysilane was added 2.4 g of aluminumsec-butoxide (Si/Al atomic ratio=58.2), and thereto was further added 31g of water while stirring. The resultant mixture was stirred at roomtemperature for 1 hour. Using a rotary evaporator, the mixture washeated to dryness under reduced pressure in an oil bath to therebyobtain a dried product, wherein the temperature of the oil bath wasinitially maintained at 70° C. and elevated to 120° C. The obtaineddried product was subjected to calcination at 200° C. for 4 hours,thereby obtaining a solid catalyst. The catalyst was subjected to apowder X-ray diffraction analysis as described above. The results of theX-ray diffraction analysis showed that the catalyst was comprised of anamorphous silica.

[0155] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 180° C. at the point in time of 12 hoursafter the start of the reaction, and further elevated to 200° C. at thepoint in time of 20 hours after the start of the reaction. 19 Hoursafter the start of the reaction, the conversion of cyclohexylamine was2% and the selectivity for ε-caprolactam was 7%; and 24 hours after thestart of the reaction, the conversion of cyclohexylamine was 3% and theselectivity for ε-caprolactam was 15%.

EXAMPLE 10

[0156] <Catalyst: Al₂O₃/SiO₂ (4)>

[0157] A catalyst was prepared in substantially the same manner as inExample 8, except that the calcination of the dried product wasperformed at 300° C. for 4 hours to obtain a solid catalyst. Theobtained catalyst was subjected to a powder X-ray diffraction analysisas described above. The results of the X-ray diffraction analysis showedthat the catalyst was comprised of an amorphous silica.

[0158] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 200° C., the temperature of thereaction vessel was once lowered to 180° C. at the point in time of 15hours after the start of the reaction and, then, elevated to 220° C. atthe point in time of 24 hours after the start of the reaction. 4 Hoursafter the start of the reaction, the conversion of cyclohexylamine was2% and the selectivity for ε-caprolactam was 6%; and 24 hours after thestart of the reaction, the conversion of cyclohexylamine was 1% and theselectivity for ε-caprolactam was 5%.

EXAMPLE 11

[0159] <Catalyst: Al₂O₃/SiO₂ (5)>

[0160] A catalyst was prepared in substantially the same manner as inExample 8, except that the calcination of the dried product wasperformed at 400° C. for 4 hours to obtain a solid catalyst. Theobtained catalyst was subjected to a powder X-ray diffraction analysisas described above. The results of the X-ray diffraction analysis showedthat the catalyst was comprised of an amorphous silica.

[0161] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 200° C., and the temperature ofthe reaction vessel was once lowered to 180° C. at the point in time of15 hours after the start of the reaction and, then, elevated to 220° C.at the point in time of 24 hours after the start of the reaction. 7Hours after the start of the reaction, the conversion of cyclohexylaminewas 2% and the selectivity for ε-caprolactam was 6%; and 29 hours afterthe start of the reaction, the conversion of cyclohexylamine was 1% andthe selectivity for ε-caprolactam was 6%.

EXAMPLE 12

[0162] <Catalyst: Al₂O₃/SiO₂ (6)>

[0163] To 4.13 g of aluminum sec-butoxide were added 121.3 g of a 10% byweight aqueous tetrapropylammonium hydroxide solution and 170 g ofwater, followed by stirring. Thereto was further added 104 g oftetraethoxysilane (Si/Al atomic ratio=30) while stirring. The resultantmixture was heated to and maintained at 60° C. and stirred at thistemperature for 30 minutes. Subsequently, the heated mixture was allowedto stand still at room temperature for 1 hour. Using a rotaryevaporator, the mixture was heated to dryness under reduced pressure inan oil bath to thereby obtain a dried product, wherein the temperatureof the oil bath was initially maintained at 60° C. and elevated to 120°C. The obtained dried product was subjected to calcination at 550° C.for 5 hours, followed by further calcination at 600° C. for 1 hour,thereby obtaining a solid catalyst. The catalyst was subjected to apowder X-ray diffraction analysis as described above. The results of theX-ray diffraction analysis showed that the catalyst was comprised of anamorphous silica. In the X-ray diffraction pattern, the amorphous silicaexhibited a broad peak at around 2 in terms of the 2θ/deg value, andthis result revealed that the amorphous silica had mesopores. Themeasurement of the pore size distribution of the catalyst also showedthat the amorphous silica contained in the catalyst had mesopores(namely pores having a pore diameter about 3 nm) as well as macropores.

[0164] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, and the temperature of the reaction vessel was maintained at195° C.

[0165] Hours after the start of the reaction, the conversion ofcyclohexylamine was 15% and the selectivity for ε-caprolactam was 36%.

EXAMPLE 13

[0166] <Catalyst: Al₂O₃/SiO₂ (6)>

[0167] A reaction was performed in substantially the same manner as inExample 1, except that the catalyst obtained in Example 12 was used asthe solid catalyst, and the temperature of the reaction vessel wasmaintained at 215° C. 6 Hours after the start of the reaction, theconversion of cyclohexylamine was 14% and the selectivity forε-caprolactam was 36%.

EXAMPLE 14

[0168] <Catalyst: Al₂O₃/SiO₂ (7)>

[0169] To 120 g of tetraethoxysilane was added 0.27 g of aluminumisopropoxide (Al[OCH(CH₃)2]3; manufactured and sold by Wako PureChemical Industries, Ltd., Japan) while stirring (Si/Al atomicratio=436), thereby obtaining an alkoxide mixture solution. The obtainedalkoxide mixture solution was added to a solution containing 9 g ofhexadecyltrimethylammonium bromide and 16.65 ml of a 20% hydrochloricacid. The resultant mixture was stirred at room temperature for 1 hour.

[0170] A 10% aqueous ammonia was dropwise added to the resultant mixtureso as to obtain a mixture having a pH of 5. The thus obtained mixturewas dried at 70 to 80° C. for 4 hours, followed by further drying at400° C. for 4 hours, thereby obtaining a dried product. The driedproduct was subjected to calcination at 550° C. for 10 hours, therebyobtaining a solid catalyst. The catalyst was subjected to a powder X-raydiffraction analysis as described above. The results of the X-raydiffraction analysis showed that the catalyst was comprised of anamorphous silica. In the X-ray diffraction pattern, the amorphous silicaexhibited a broad peak at around 2 to 3 in terms of the 2θ/deg value.Further, the measurement of the pore size distribution of the catalystshowed that the amorphous silica contained in the catalyst had a widepore diameter distribution wherein the pore diameter ranged from 2 to 15nm.

[0171] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, and the temperature of the reaction vessel was maintained at215° C. 4 Hours after the start of the reaction, the conversion ofcyclohexylamine was 41% and the selectivity for ε-caprolactam was 18%.

EXAMPLE 15

[0172] <Catalyst: Al₂O₃/SiO₂ (8)>

[0173] A catalyst was prepared in substantially the same manner as inExample 14, except that 0.55 g of aluminum isopropoxide (Si/Al atomicratio=214) was used. The catalyst was subjected to a powder X-raydiffraction analysis as described above. The results of the X-raydiffraction analysis showed that the catalyst was comprised of anamorphous silica. In the X-ray diffraction pattern, the amorphous silicaexhibited a broad peak at around 2 to 3 in terms of the 2θ/deg value.Further, the measurement of the pore size distribution of the catalystshowed that the amorphous silica contained in the catalyst had a widepore diameter distribution wherein the pore diameter ranged from 2 to 15nm.

[0174] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, and the temperature of the reaction vessel was maintained at215° C. 7 Hours after the start of the reaction, the conversion ofcyclohexylamine was 40% and the selectivity for ε-caprolactam was 28%.

EXAMPLE 16

[0175] <Catalyst: Al₂O₃/SiO₂ (9)>

[0176] A catalyst was prepared in substantially the same manner as inExample 14, except that 1.32 g of aluminum isopropoxide (Si/Al atomicratio=89) was used. The prepared catalyst was subjected to a powderX-ray diffraction analysis as described above. The results of the X-raydiffraction analysis showed that the catalyst was comprised of anamorphous silica. In the X-ray diffraction pattern, the amorphous silicaexhibited a broad peak at around 2 to 3 in terms of the 2θ/deg value.Further, the measurement of the pore size distribution of the catalystshowed that the amorphous silica contained in the catalyst had a widepore diameter distribution wherein the pore diameter ranged from 2 to 15nm.

[0177] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, and the temperature of the reaction vessel was maintained at215° C. 7 Hours after the start of the reaction, the conversion ofcyclohexylamine was 41% and the selectivity for ε-caprolactam was 26%.

EXAMPLE 17

[0178] <Catalyst: Al₂O₃/SiO₂ (8)>

[0179] A reaction was performed in substantially the same manner as inExample 1, except that the catalyst obtained in Example 14 was used asthe solid catalyst, and the temperature of the reaction vessel wasmaintained at 160° C. 18 Hours after the start of the reaction, theconversion of cyclohexylamine was 19% and the selectivity forε-caprolactam was 3%.

EXAMPLE 18

[0180] <Catalyst: MCM-41 (1) (Mesoporous Substance)>

[0181] To 21.8 g of a 15% aqueous solution of tetramethylammoniumhydroxide ((CH₃)₄NOH; manufactured and sold by Wako Pure ChemicalIndustries, Ltd., Japan) were added 0.48 g of a 85% sodium hydroxidereagent and 15.4 g of cetyltrimethylammonium bromide[CH₃(CH₂)₁₅N(CH₃)₃]Br; manufactured and sold by Wako Pure ChemicalIndustries, Ltd., Japan), thereby obtaining solution A. On the otherhand, 11.14 g of tetraethoxysilane was mixed with 100 g of water,thereby obtaining solution B. Solution B was dropwise added to solutionA while stirring solution A. The resultant mixture was stirred for 1hour. Subsequently, the mixture was transferred to an autoclave,followed by hydrothermal synthesis at 100° C. for 2 days, to therebyobtain a slurry. The obtained slurry was subjected to filtration, andthe resultant filtration residue was washed with an ion exchanged water,followed by drying at 110° C. for 5 hours, to thereby obtain a driedproduct. The obtained dried product was subjected to calcination at 550°C. for 8 hours, thereby obtaining a solid catalyst.

[0182] The obtained catalyst was subjected to a powder X-ray diffractionanalysis as described above. In the X-ray diffraction pattern, a peakascribed to mesopores was observed at 2 in terms of the 2θ/deg value,and this diffraction pattern was the same as that of MCM-41. The poresize distribution of the catalyst was measured as mentioned above. Asharp peak was observed in the pore diameter range of from 2 nm to 3 nm,and it was confirmed that the catalyst was MCM-41.

[0183] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 170° C. at the point in time of 22 hoursafter the start of the reaction, and further elevated to 180° C. at thepoint in time of 28 hours after the start of the reaction. 16 Hoursafter the start of the reaction, the conversion of cyclohexylamine was17% and the selectivity for ε-caprolactam was 9%; and 36 hours after thestart of the reaction, the conversion of cyclohexylamine was 9% and theselectivity for ε-caprolactam was 9%.

EXAMPLE 19

[0184] <Catalyst: MCM-41 (2) (Mesoporous Substance)>

[0185] A catalyst was prepared in substantially the same manner as inExample 18, except that the hydrothermal synthesis was conducted for 3days. The results of the powder X-ray diffraction analysis and the poresize distribution measurement confirmed that the catalyst was MCM-41.

[0186] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 180° C. at the point in time of 22 hoursafter the start of the reaction, further elevated to 200° C. at thepoint in time of 32 hours after the start of the reaction, and furtherelevated to 220° C. at the point in time of 48 hours after the start ofthe reaction. 17 Hours after the start of the reaction, the conversionof cyclohexylamine was 13% and the selectivity for ε-caprolactam was 6%;25 hours after the start of the reaction, the conversion ofcyclohexylamine was 22% and the selectivity for ε-caprolactam was 8%; 39hours after the start of the reaction, the conversion of cyclohexylaminewas 12% and the selectivity for ε-caprolactam was 14%; and 53 hoursafter the start of the reaction, the conversion of cyclohexylamine was14% and the selectivity for ε-caprolactam was 14%.

EXAMPLE 20

[0187] <Catalyst: W-MCM-41 (1) (Mesoporous Substance)>

[0188] To 21.9 g of a 15% aqueous tetramethylammonium hydroxide solutionwere added 0.48 g of a 85% sodium hydroxide reagent and 15.4 g ofcetyltrimethylammonium bromide, thereby obtaining solution A. On theother hand, 0.1448 g of ammonium metatungstate ((NH₄)₆W₁₂O₃₉;manufactured and sold by Sigma-Aldrich Co., U.S.A.) was dissolved in 100g of water, and thereto was added 11.14 g of tetraethoxysilane (Si/Watomic ratio=90), thereby obtaining solution B. Solution B was dropwiseadded to solution A while stirring solution A.

[0189] The resultant mixture was stirred for 1 hour. Subsequently, themixture was transferred to an auto-clave, followed by hydrothermalsynthesis at 100° C. for 2 days, to thereby obtain a slurry. Theobtained slurry was subjected to filtration, and the resultantfiltration residue was washed with an ion exchanged water, followed bydrying at 110° C. for 5 hours, to thereby obtain a dried product. Theobtained dried product was subjected to calcination at 550° C. for 8hours, thereby obtaining a solid catalyst. The results of the powderX-ray diffraction analysis and the pore size distribution measurementconfirmed that the catalyst was MCM-41.

[0190] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 180° C. at the point in time of 19 hoursafter the start of the reaction, and further elevated to 200° C. at thepoint in time of 28 hours after the start of the reaction. 16 Hoursafter the start of the reaction, the conversion of cyclohexylamine was7% and the selectivity for ε-caprolactam was 5%; 22 hours after thestart of the reaction, the conversion of cyclohexylamine was 8% and theselectivity for ε-caprolactam was 8%; and 29 hours after the start ofthe reaction, the conversion of cyclohexylamine was 11% and theselectivity for ε-caprolactam was 22%.

EXAMPLE 21

[0191] <Catalyst: W-MCM-41 (2) (Mesoporous Substance)>

[0192] A catalyst was prepared in substantially the same manner as inExample 20, except that 0.0724 g of ammonium metatungstate was used forpreparing solution B (Si/W atomic ratio=181). The results of the powderX-ray diffraction analysis and the pore size distribution measurementconfirmed that the catalyst was MCM-41.

[0193] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., and the temperature ofthe reaction vessel was elevated to 180° C. at the point in time of 22hours after the start of the reaction, and further elevated to 200° C.at the point in time of 32 hours after the start of the reaction. 16Hours after the start of the reaction, the conversion of cyclohexylaminewas 23% and the selectivity for ε-caprolactam was 8%; 26 hours after thestart of the reaction, the conversion of cyclohexylamine was 25% and theselectivity for ε-caprolactam was 10%; and 34 hours after the start ofthe reaction, the conversion of cyclohexylamine was 30% and theselectivity for ε-caprolactam was 17%.

EXAMPLE 22

[0194] <Catalyst: W-MCM-41 (3) (Mesoporous Substance)>

[0195] A catalyst was prepared in substantially the same manner as inExample 20, except that 0.0362 g of ammonium metatungstate was used forpreparing solution B (Si/W atomic ratio=362). The results of the powderX-ray diffraction analysis and the pore size distribution measurementconfirmed that the catalyst was MCM-41.

[0196] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 170° C. at the point in time of 23 hoursafter the start of the reaction, and further elevated to 180° C. at thepoint in time of 29 hours after the start of the reaction. 41 Hoursafter the start of the reaction, the conversion of cyclohexylamine was18% and the selectivity for ε-caprolactam was 14%.

EXAMPLE 23

[0197] <Catalyst: W-MCM-41 (4) (Mesoporous Substance)>

[0198] A catalyst was prepared in substantially the same manner as inExample 20, except that 0.0270 g of ammonium metatungstate was used forpreparing solution B (Si/W atomic ratio=485). The results of the powderX-ray diffraction analysis and the pore size distribution measurementconfirmed that the catalyst was MCM-41.

[0199] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature waselevated to 180° C. at the point in time of 12 hours after the start ofthe reaction, and further elevated to 200° C. at the point in time of 21hour after the start of the reaction. 41 Hours after the start of thereaction, the conversion of cyclohexylamine was 18% and the selectivityfor ε-caprolactam was 14%; 20 hours after the start of the reaction, theconversion of cyclohexylamine was 11% and the selectivity forε-caprolactam was 8.%; and 26 hours after the start of the reaction, theconversion of cyclohexylamine was 13% and the selectivity forε-caprolactam was 15%.

EXAMPLE 24

[0200] <Catalyst: Al-HMS (1) (Mesoporous Substance)>

[0201] “HMS” is an abbreviation for hexagonal mesoporous silica. HMS isknown to have an irregular and disordered structure and it is clearlydistinct from MCM-41. In this Example, HMS was prepared as follows. To50 g of water were added 160 g of ethanol and 20 g of dodecylamine(CH₃(CH₂)₁₁NH₂; manufactured and sold by Wako Pure Chemical Industries,Ltd., Japan) in this order, thereby obtaining a solution. 83 g oftetraethoxysilane was dropwise added to the obtained solution whilestirring. Thereto was further added an aluminum isopropoxide solutionobtained by dissolving 3.27 g of aluminum isopropoxide in 10 g ofisopropanol (Si/Al atomic ratio=30), wherein the aluminum isopropoxidesolution was dropwise added to the above-obtained mixture whilestirring. The resultant mixture was stirred at room temperature for 30minutes and, then, allowed to stand still at room temperature for 20hours, thereby obtaining a slurry.

[0202] The above-obtained slurry was subjected to filtration, and theresultant filtration residue was washed with an ion exchanged water,followed by drying at 115° C. for 5 hours, to thereby obtain a driedproduct. The obtained dried product was washed with ethanol to therebyremove most of the residual dodecylamine. Subsequently, the washedproduct was subjected to calcination in an electric kiln at 300° C. for2 hours and, then, the temperature was elevated at a rate of 1° C./minto 550° C. and maintained at 550° C. for 4 hours, thereby obtaining asolid catalyst.

[0203] The obtained catalyst was subjected to a powder X-ray diffractionanalysis as described above. In the X-ray diffraction pattern, a peakascribed to mesopores was observed at around 2 in terms of the 2θ/degvalue. Further, the pore size distribution of the catalyst was measuredas mentioned above. A sharp peak was observed in the pore diameter rangeof from 3 nm to 4 nm, and it was confirmed that the obtained catalystwas HMS.

[0204] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, and the temperature of the reaction vessel was maintained at190° C. 8 Hours after the start of the reaction, the conversion ofcyclohexylamine was 35% and the selectivity for δ-caprolactam was 11%.

EXAMPLE 25

[0205] <Catalyst: Al-HMS (2) (Mesoporous Substance)>

[0206] A catalyst was prepared in substantially the same manner as inExample 24, except that 1.98 g of aluminum isopropoxide (Si/Al atomicratio=50) was used. The results of the powder X-ray diffraction analysisand the pore size distribution measurement confirmed that the catalystwas HMS.

[0207] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, and the temperature of the reaction vessel was maintained at190° C. 9 Hours after the start of the reaction, the conversion ofcyclohexylamine was 33% and the selectivity for ε-caprolactam was 17%.

EXAMPLE 26

[0208] <Catalyst: Al-HMS (3) (Mesoporous Substance)>

[0209] A catalyst was prepared in substantially the same manner as inExample 24, except that 1.40 g of aluminum isopropoxide (Si/Al atomicratio=70) was used. The results of the powder X-ray diffraction analysisand the pore size distribution measurement confirmed that the catalystwas HMS.

[0210] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, and the temperature of the reaction vessel was maintained at190° C. 7 Hours after the start of the reaction, the conversion ofcyclohexylamine was 33% and the selectivity for ε-caprolactam was 7%.

EXAMPLE 27

[0211] <Catalyst: SAPO-11 (Phosphate Zeolite)>

[0212] 276.0 g of water and 88.5 g of a 85% by weight aqueous phosphatesolution were mixed together, and thereto was added 156.5 g of aluminumisopropoxide, followed by stirring. 3.1 g of powdery silica was added tothe mixture, followed by stirring, thereby obtaining a homogenousmixture. Thereto was further added 49.1 g of di-n-propylamine((CH₃CH₂CH₂)₂NH; manufactured and sold by Wako Pure Chemical Industries,Ltd., Japan) and further stirred until a homogeneous mixture wasobtained. The thus obtained homogeneous mixture was transferred to a1-liter autoclave, followed by hydrothermal synthesis at 150° C. for 133hours, thereby obtaining a slurry. The obtained slurry was subjected tofiltration, and the resultant filtration residue was washed with an ionexchanged water, followed by drying, thereby obtaining a dried product.The dried product was calcined in air at 500° C. for 2 hours, therebyobtaining a calcined, crystalline powder.

[0213] The obtained crystalline powder was subjected to a powder X-raydiffraction analysis as described above. From the X-ray diffractionpattern, the crystalline powder was confirmed to besilicoaluminophophate SAPO-11. The crystalline powder was furthersubjected to an energy dispersive X-ray analysis. As a result, it wasfound that the (P₂O₅+Al₂O₃)/SiO₂ molar ratio of the crystalline powderwas 7.8.

[0214] The calcined, crystalline powder (SAPO-11) was added to a 1 Naqueous ammonium nitrate solution to thereby obtain a 10% by weightSAPO-11 slurry, and the obtained slurry was subjected to an ion exchangetreatment at room temperature for 3 hours. The resultant slurry wassubjected to filtration, and the resultant filtration residue was washedwith an ion exchanged water, followed by drying at 120° C. for 10 hours,to thereby obtain a dried product. The obtained dried product wassubjected to calcination at 530° C. for 3 hours, thereby obtaining anH-type SAPO-11 catalyst.

[0215] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 180° C. at the point in time of 24 hoursafter the start of the reaction, and further elevated to 220° C. at thepoint in time of 33 hours after the start of the reaction. 18 Hoursafter the start of the reaction, the conversion of cyclohexylamine was2% and the selectivity for ε-caprolactam was 2%; 26 hours after thestart of the reaction, the conversion of cyclohexylamine was 2% and theselectivity for ε-caprolactam was 4%; and 40 hours after the start ofthe reaction, the conversion of cyclohexylamine was 3% and theselectivity for ε-caprolactam was 4%.

EXAMPLE 28

[0216] <Catalyst: SAPO-34 (Phosphate Zeolite)>

[0217] 146.7 g of water and 95.9 g of a 85% by weight aqueous phosphatesolution were mixed together, and thereto was added 169.6 g of aluminumisopropoxide, followed by stirring. 1.6 g of a silica powder was addedto the mixture, followed by stirring, to thereby obtain a homogenousmixture. Thereto was added 305.2 g of a 20% by weight aqueous solutionof tetraethylammonium hydroxide ((C₂H₅)₄NOH; manufactured and sold byWako Pure Chemical Industries, Ltd., Japan) and further stirred until ahomogeneous mixture was obtained.

[0218] The thus obtained homogeneous mixture was transferred to a1-liter autoclave, followed by hydrothermal synthesis at 150° C. for 133hours, thereby obtaining a slurry. The obtained slurry was subjected tofiltration, and the resultant filtration residue was washed with an ionexchanged water, followed by drying, thereby obtaining a dried product.The dried product was calcined in air at 500° C. for 2 hours, therebyobtaining a calcined, crystalline powder. The obtained crystallinepowder was subjected to a powder X-ray diffraction analysis as describedabove. From the X-ray diffraction pattern, the crystalline powder wasconfirmed to be silicoaluminophophate SAPO-34. The crystalline powderwas further subjected to an energy dispersive X-ray analysis. It wasfound that the (P₂O₅+Al₂O₃)/SiO₂ molar ratio of the catalyst was 16.4.

[0219] The calcined, crystalline powder (SAPO-34) was added to a 1 Naqueous ammonium nitrate solution to thereby obtain a 10% by weightslurry of SAPO-34, and the obtained slurry was subjected to ion exchangetreatment at room temperature for 3 hours. The resultant slurry wassubjected to filtration, and the resultant filtration residue was washedwith an ion exchanged water, followed by drying at 120° C. for 10 hours,to thereby obtain a dried product. The obtained dried product wassubjected to calcination at 530° C. for 3 hours, thereby obtaining anH-type SAPO-34 catalyst.

[0220] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 180° C. at the point in time of 24 hoursafter the start of the reaction, and further elevated to 220° C. at thepoint in time of 33 hours after the start of the reaction. 12 Hoursafter the start of the reaction, the conversion of cyclohexylamine was1% and the selectivity for ε-caprolactam was 3%; 30 hours after thestart of the reaction, the conversion of cyclohexylamine was 1% and theselectivity for ε-caprolactam was 4%; and 40 hours after the start ofthe reaction, the conversion of cyclohexylamine was 1% and theselectivity for ε-caprolactam was 3%.

EXAMPLE 29

[0221] <Catalyst: Silicalite-1 (Zeolite)>

[0222] To 130.0 g of tetraethoxysilane was added 278.2 g of ethanol, andthereto was further added 241.8 g of a 10% by weight aqueoustetrapropylammonium hydroxide solution. The resultant mixture wasstirred using a homogenizer at a revolution rate of 5,000 rpm for 20minutes. Subsequently, the homogenized mixture was transferred to a1-liter autoclave, followed by hydrothermal synthesis at 100° C. for 5days, thereby obtaining a slurry. The obtained slurry was subjected tofiltration, and the resultant filtration residue was washed with an ionexchanged water, followed by drying at 110° C. for 5 hours, therebyobtaining a dried product. The obtained dried product was subjected tocalcination at 530° C. for 3 hours, thereby obtaining a catalyst. Theobtained catalyst was subjected to a powder X-ray diffraction analysisas described above. From the X-ray diffraction pattern, the catalyst wasconfirmed to be silicalite-1.

[0223] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, the reaction was started at 160° C., the temperature of thereaction vessel was elevated to 180° C. at the point in time of 22 hoursafter the start of the reaction, and further elevated to 200° C. at thepoint in time of 32 hours after the start of the reaction. 20 Hoursafter the start of the reaction, the conversion of cyclohexylamine was5% and the selectivity for ε-caprolactam was 9%; 30 hours after thestart of the reaction, the conversion of cyclohexylamine was 6% and theselectivity for ε-caprolactam was 22%; and 38 hours after the start ofthe reaction, the conversion of cyclohexylamine was 7% and theselectivity for ε-caprolactam was 28%.

EXAMPLE 30

[0224] <Catalyst: Silicalite-1 (Zeolite)>

[0225] A reaction was performed in substantially the same manner as inExample 1, except that the catalyst obtained in Example 29 was used asthe solid catalyst, and the temperature of the reaction vessel wasmaintained at 190° C. 10 Hours after the start of the reaction, theconversion of cyclohexylamine was 6% and the selectivity forε-caprolactam was 30%.

EXAMPLE 31

[0226] <Catalyst: Silicalite-2 (Zeolite)>

[0227] To 102.0 g of silicon oxide hydrate (SiO₂.nH₂O; manufactured andsold by Wako Pure Chemical Industries, Ltd., Japan) was added 129.7 g ofa 10% by weight aqueous solution of tetrabutylammonium hydroxide([CH₃(CH₂)₃]₄NOH; manufactured and sold by Wako Pure ChemicalIndustries, Ltd., Japan), followed by stirring. Thereto were added 75.0g of a 28% aqueous ammonia while stirring, followed by addition of 228.1g of water. The stirring of the resultant mixture was continued at roomtemperature for 1 hour. The resultant mixture was transferred to a1-liter autoclave, followed by hydrothermal synthesis at 170° C. for 3days, to thereby obtain a slurry. The obtained slurry was subjected tofiltration, and the resultant filtration residue was washed with an ionexchanged water, followed by drying at 100° C. for 4 hours, therebyobtaining a dried product. The obtained dried product was subjected tocalcination at 550° C. for 8 hours, thereby obtaining a catalyst. Theobtained catalyst was subjected to a powder X-ray diffraction analysisas described above. From the X-ray diffraction pattern, the catalyst wasconfirmed to be silicalite-2.

[0228] A reaction was performed in substantially the same manner as inExample 1, except that the obtained catalyst was used as the solidcatalyst, and the temperature of the reaction vessel was maintained at195° C. 6 Hours after the start of the reaction, the conversion ofcyclohexylamine was 6% and the selectivity for ε-caprolactam was 25%.

EXAMPLE 32

[0229] <Catalyst: Silicalite-2 (Zeolite)>

[0230] A reaction was performed in substantially the same manner as inExample 1, except that the catalyst obtained in Example 31 was used asthe solid catalyst, and the temperature of the reaction vessel wasmaintained at 215° C. 3 Hours after the start of the reaction, theconversion of cyclohexylamine was 8% and the selectivity forε-caprolactam was 41%.

EXAMPLE 33

[0231] <Catalyst: Silicalite-2 (Zeolite)>

[0232] A reaction was performed in substantially the same manner as inExample 1, except that the catalyst obtained in Example 31 was used asthe solid catalyst, and the temperature of the reaction vessel wasmaintained at 230° C. 3 Hours after the start of the reaction, theconversion of cyclohexylamine was 9% and the selectivity forε-caprolactam was 37%.

EXAMPLE 34

[0233] <Catalyst: Silicalite-2 (Zeolite)>

[0234] A reaction was performed in substantially the same manner as inExample 1, except that the catalyst obtained in Example 31 was used asthe solid catalyst, and the temperature of the reaction vessel wasmaintained at 250° C. 2 Hours after the start of the reaction, theconversion of cyclohexylamine was 12% and the selectivity forε-caprolactam was 26%.

EXAMPLE 35

[0235] A reaction was performed using the catalyst prepared in Example15. The reaction vessel used for performing the reaction was a tubularreactor (outer diameter: 25.4 mm, inner diameter: 23.00 mm, length: 700mm) which was made of SUS316 and which was provided with a sheath tubefor inserting a thermocouple therein, wherein the thermocouple was usedto measure the temperature of a catalyst layer formed inside thereaction vessel; and a layer of SUS316 fillers for vaporizingcyclohexylamine, which layer is provided above the catalyst layer. Thereaction vessel was placed in a heating furnace for heating the reactionvessel, wherein the heating furnace had three heating stages (upper,middle and lower heating stages).

[0236] The above-mentioned reaction vessel was charged with 40 g of thecatalyst prepared in Example 15. The reaction vessel had attachedthereto two traps (1st trap and 2nd trap) for condensing the gaseousreaction mixture obtained from an outlet of the reaction vessel, whereineach of the traps were provided with a jacket and the 1st and 2nd trapswere maintained at 70° C. and ° C., respectively. After purging thereaction vessel with nitrogen gas, the reaction vessel was heated to andmaintained at 215° C. The reaction was started by feeding liquidcyclohexylamine, oxygen and nitrogen into the reaction vessel, whereincyclohexylamine was fed at 25° C. at a flow rate of 0.1 ml/min, andoxygen and nitrogen were fed at 28 cc/min and 372 cc/min, respectively.The composition of the mixture of cyclohexylamine, oxygen and nitrogenaround the inlet of the catalyst layer became: cyclohexylamine=5.1% byvolume, oxygen=6.6% by volume, and nitrogen=88.3% by volume. The SVvalue was 272 h⁻¹.

[0237] The reaction was continued for 48 hours, and 268 g of a liquidreaction mixture was collected in total from the 1st and 2nd traps. Thecollected reaction mixture contained 26 g of ε-caprolactam. Afterrepeating the distillation of the reaction mixture, ε-caprolactam waspurified by crystal deposition using cyclohexane as a solvent. Thepurity of the thus obtained ε-caprolactam, as measured by means of GC,was 99.9%.

EXAMPLE 36

[0238] <Synthesis of Cyclohexylamine by an Amination Reaction ofCyclohexanol>

[0239] To an aqueous solution obtained by dissolving 47 g of coppersulfate trihydrate and 16 g of nickel nitrate hexahydrate in 250 ml ofwater was added, followed by stirring. The resultant mixture was heatedto and maintained at 80° C. by means of a water bath, and thereto wasdropwise added 250 ml of an aqueous sodium carbonate solution(containing 42 g of sodium carbonate) over 2 hours while stirring. Theresultant mixture was subjected to aging for 5 hours, to thereby obtaina slurry. The obtained slurry was subjected to filtration, and theresultant filtration residue was repeatedly washed with warm water,followed by drying at about 100° C. for one day, thereby obtaining adried product. The dried product was pulverized using a mortar. Theresultant pulverized product was charged into a quartz glass tube andcalcined in air at 350° C. for 3 hours, thereby obtaining acopper-nickel/γ-alumina catalyst.

[0240] The above-obtained copper-nickel/γ-alumina catalyst was shapedinto particles and charged into a tubular reactor made of stainlesssteel. Hydrogen gas was fed into the reactor at a rate of 150 ml/min,while maintaining the temperature of the catalyst phase at 350° C., tothereby perform an activation treatment of the catalyst for 3 hours.After the activation treatment, the temperature of the reactor waslowered to 180° C., and into the reactor was fed a gaseous feedstockmixture (which had a cyclohexanol:ammonia:hydrogen molar ratio of1:5:3). The feeding of the gaseous feedstock mixture was performed underatmospheric pressure and under conditions wherein the LSV value became0.1 liter/liter of catalyst/hour. The reaction was continued for 5hours. The reaction product was analyzed by GC, and it was found thatthe conversion of cyclohexanol was 99.0% and the selectivity forcyclohexylamine was 96.1%.

EXAMPLE 37

[0241] <Recycling of the By-Products of the Oxidation Reaction ofCyclohexylamine to the Amination Reaction System>

[0242] 50 g of cyclohexanol was mixed with 10 g of a dilute obtained inExample 35 during the distillation performed to purify ε-caprolactamseparated from the collected reaction mixture, to thereby obtain amixture. The dilute contained the following by-products: 22% ofcyclohexanone, 74% of N-cyclohexylidene cyclohexylamine and 4% of othercompounds. Using the obtained mixture, an amination reaction wasperformed under the same conditions as used in Example 36. As a result,it was found that the conversion of the by-products was 98.3% and theselectivity for cyclohexylamine was 97.1%.

INDUSTRIAL APPLICABILITY

[0243] The method of the present invention not only prevents theby-production of ammonium sulfate which is of little commercial value,but also needs no cumbersome operations involved in conventional methodsfor producing a lactam, such as synthesis of hydroxylamine salt (whichcan be obtained only by a process involving complicated steps) andcirculation of a buffer solution, and involves no step of producingintermediate oxime, which should be followed by an oxime purificationoperation, and, hence, a lactam can be produced from an alicyclicprimary amine very easily.

[0244] The lactam produced by the method of the present invention is auseful compound as a raw material for polymers, pharmaceuticals,agricultural chemicals and the like in the field of organic chemicalindustry. Especially, in the case where the lactam is ε-caprolactam, itis used for producing fibers and resins and it is useful as a rawmaterial for nylon 6.

1. A method for producing a lactam, which comprises subjecting analicyclic primary amine to an oxidation reaction in the gaseous phase inthe presence of molecular oxygen and a catalyst comprising a siliconoxide, to thereby obtain a lactam, and separating said lactam from areaction system of said oxidation reaction. 2 through
 4. (Cancelled) 5.The method according to any claim 1, wherein said catalyst furthercomprises at least one element selected from the group consisting oflithium, sodium, potassium, rubidium, cesium, magnesium, calcium,strontium, barium, titanium, zirconium, vanadium, niobium, tantalum,molybdenum, tungsten, manganese, iron, cobalt, nickel, copper, zinc,silver, boron, aluminum, gallium, tin, phosphorus, antimony and bismuth.6. The method according to claim 1, wherein said catalyst is a zeolite.7. The method according to claim 6, wherein said zeolite is selectedfrom the group consisting of silicalite-1 and silicalite-2.
 8. Themethod according to claim 1, wherein said catalyst comprises anamorphous silicon oxide as said silicon oxide.
 9. The method accordingto claim 8, wherein said catalyst further comprises aluminum.
 10. Themethod according to claim 8, wherein said amorphous silicon oxide hasmesopores.
 11. The method according to claim 10, wherein said amorphoussilicon oxide having mesopores is selected from the group consisting ofMCM-41 and HMS.
 12. The method according to claim 10, wherein saidamorphous silicon oxide having mesopores is produced by adding to asilicon alkoxide a quaternary ammonium salt.
 13. The method according toclaim 12, wherein said quaternary ammonium salt is cetyltrimethylammonium salt.
 14. The method according to any one of claims 1 and 5 to13, wherein, said alicyclic primary amine is obtained by subjecting toan amination reaction at least one compound selected from the groupconsisting of an alicyclic alcohol and an alicyclic ketone.
 15. Themethod according to claim 14, wherein at least a part of one or moreby-products formed in said oxidation reaction is recycled to a reactionsystem of said amination reaction.
 16. The method according to claim 1,wherein said alicyclic primary amine is cyclohexylamine, and said lactamis ε-caprolactam.
 17. The method according to claim 14, wherein said atleast one compound selected from the group consisting of an alicyclicalcohol and an alicyclic ketone is selected from the group consisting ofcyclohexanol and cyclohexanone, said alicyclic primary amine iscyclohexylamine, and said lactam is ε-caprolactam.
 18. A catalyst foruse in producing a lactam by subjecting an alicyclic primary amine to anoxidation reaction, which comprises a silicon oxide.
 19. The catalystaccording to claim 18, which further comprises at least one elementselected from the group consisting of lithium, sodium, potassium,rubidium, cesium, magnesium, calcium, strontium, barium, titanium,zirconium, vanadium, niobium, tantalum, molybdenum, tungsten, manganese,iron, cobalt, nickel, copper, zinc, silver, boron, aluminum, gallium,tin, phosphorus, antimony and bismuth.
 20. The catalyst according toclaim 18, which is a zeolite.
 21. The catalyst according to claim 20,which is a zeolite selected from the group consisting of silicalite-1and silicalite-2.
 22. The catalyst according to claim 18, whichcomprises an amorphous silicon oxide as said silicon oxide.
 23. Thecatalyst according to claim 22, which further comprises aluminum. 24.The catalyst according to claim 22, wherein said amorphous silicon oxidehas mesopores.
 25. The catalyst according to claim 24, wherein saidamorphous silicon oxide having mesopores is a selected from the groupconsisting of MCM-41 and HMS.
 26. The catalyst according to claim 24,wherein said amorphous silicon oxide having mesopores is produced byadding to a silicon alkoxide a quaternary ammonium salt.
 27. Thecatalyst according to claim 26, wherein said quaternary ammonium salt iscetyltrimethyl ammonium salt.